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Abstract:

A gas operating system for a firearm renders the firearm capable of
firing a wide range of shot loads by passively or automatically
compensating for different shot loads. The firearm includes a plurality
of ports formed in the firearm barrel, and corresponding ports formed in
a gas cylinder of the gas operating system. The ports tap gases generated
during firing which are used to cycle the firearm. When firing different
cartridge loads, differing combinations of the ports are selectively at
least partially blocked or otherwise obstructed by the cartridge casing
according to the size of the cartridge.

Claims:

1-17. (canceled)

18. A firearm, comprising: a receiver; a firing mechanism; a barrel
having a firing chamber; a plurality of ports extending through the
barrel and opening into the firing chamber; a bolt having a locking
position in which the bolt is adjacent to a first end of the barrel; and
a gas operating system, wherein the gas operating system comprises a gas
cylinder having at least one piston bore in fluid communication with the
barrel through at least one of the plurality of ports in the barrel;
wherein the plurality of ports in the barrel are arranged at varying
locations along the length of the barrel from the firing chamber such
that cartridges of different lengths can at least partially obscure one
or more of the ports to vary flows of gases transmitted to the gas
cylinder of the gas operating system.

19. The firearm of claim 18, wherein at least a first port of the
plurality of ports is at a first distance from the first end of the
barrel, and at least a second port of the plurality of ports is at a
second distance from the first end of the barrel that is greater that the
first distance.

20. The firearm of claim 19, wherein at least a third port of the
plurality of ports is at a third distance from the first end of the
barrel that is greater than the second distance.

21. The firearm of claim 18, wherein the at least one piston bore
comprises a first piston bore and a second piston bore.

22. The firearm of claim 18, wherein the barrel comprises a frustoconical
constriction between the plurality of ports and a second end of the
barrel.

23. The firearm of claim 18, wherein the gas operating system further
comprises at least one pusher piston rod axially translatable within the
at least one piston bore.

24. The firearm of claim 18, wherein the gas cylinder is joined to an
underside of the barrel, and wherein the gas cylinder comprises a
plurality of ports, one each of the ports in the gas cylinder being
aligned with a corresponding one of the ports in the barrel.

25. The firearm of claim 18, wherein the ports in the barrel extend
through the barrel at a nonzero angle with respect to a longitudinal axis
of the barrel.

26. A firearm, comprising: a receiver; a firing mechanism; a barrel
having a firing chamber at a first end of the barrel; a plurality of
ports extending through the barrel; a gas operating system comprising a
gas cylinder, wherein at least a first port of the plurality of ports is
located along the barrel at a first distance from the first end of the
barrel, and at least a second port of the plurality of ports is located
along the barrel at a second distance from the first end of the barrel,
wherein the second distance is greater than the first distance.

27. The firearm of claim 26, wherein at least a third port of the
plurality of ports is at a third distance from the first end of the
barrel that is greater than the second distance.

28. The firearm of claim 26 wherein the gas cylinder comprises a first
piston bore and a second piston bore.

29. The firearm of claim 28, wherein the gas operating system further
comprises a first pusher piston axially translatable within the first
piston bore.

30. The firearm of claim 26, wherein the barrel comprises a frustoconical
constriction between the plurality of ports and a second end of the
barrel.

31. The firearm of claim 26, wherein the gas cylinder is joined to an
underside of the barrel, and wherein the gas cylinder comprises a
plurality of ports, one each of the ports in the gas cylinder being
aligned with a corresponding one of the ports in the barrel.

32. The firearm of claim 26, wherein the ports in the barrel extend
through the barrel at a nonzero angle with respect to a longitudinal axis
of the barrel.

33. A method of operating a firearm, comprising: loading a firearm
comprising: a receiver; a firing mechanism; a barrel having a firing
chamber; a plurality of ports extending through the barrel and opening
into the firing chamber; and a gas operating system, with a cartridge,
the cartridge having a case of a predetermined length; chambering the
cartridge in the firing chamber; actuating the firing mechanism to fire
the cartridge, wherein as the cartridge is fired, the case extends
axially in the firing chamber, and at least partially covers at least one
of the plurality of ports so as to at least partially prevent a portion
of gases generated from firing t pass through the at least one of the
plurality of ports in the barrel to control operation of the gas
operating system of the firearm.

34. The method of claim 33, wherein the ports in the barrel extend
through the barrel at a nonzero angle with respect to a longitudinal axis
of the barrel.

35. A method of operating a firearm, comprising: loading a cartridge
having a case within a firearm comprising: a receiver; a firing
mechanism; a barrel having a firing chamber at a first end of the barrel;
a plurality of ports extending through the barrel, the plurality of ports
comprising a first port at a first distance from the first end of the
barrel, a second port at a second distance from the first end of the
barrel that is greater than the first distance, and a third port at a
third distance from the first end of the barrel that is greater than the
second distance; chambering the cartridge in the firing chamber;
actuating the firing mechanism to fire the cartridge, wherein as the
cartridge is fired, the case extends axially along the firing chamber,
and at least partially prevents part of the gases generated from firing
from passing through at least one of the plurality of ports.

36. The method of claim 35, wherein as the case extends axially the case
at least partially prevents part of the gases generated from firing to
pass through the second port.

37. The method of claim 35, wherein the ports in the barrel extend
through the barrel at a nonzero angle with respect to a longitudinal axis
of the barrel.

38. A method of manufacturing a barrel component for a firearm,
comprising: providing a barrel having a firing chamber, a muzzle end, a
cylindrical portion, and a constriction between the firing chamber and
the cylindrical portion; providing a gas cylinder; securing the gas
cylinder to the barrel; and forming a plurality of spaced apertures
through the gas cylinder and the barrel at spaced locations therealong,
with the apertures located along the barrel at different distances from
the firing chamber of the barrel so as to be selectively closeable by a
cartridge received within the firing chamber, and wherein a first end of
each aperture opens into the firing chamber.

39. The method of claim 38, wherein the aperture is oriented at a nonzero
angle with respect to a longitudinal axis of the barrel.

Description:

[0003] The present invention generally relates to a gas operating system
for firearms that allows firing of different cartridge loads for a given
shell caliber or gauge.

[0004] 2. Related Art

[0005] Automatic and semiautomatic shotguns having user-adjustable gas
systems are known. Adjustable gas systems allow a user to control the
amount of gas entering into and/or vented from the system, which allows a
wider range of cartridge loads to be fired from a single firearm.
However, if an adjustable gas system is set for heavy loads and the
weapon is used to fire light loads, the firearm may not fully cycle,
which may require the user to manually cycle the bolt in order to load
the next round. If the adjustable gas system is set for light loads and
the weapon is used to fire a heavy load, the bolt velocity after firing
may result in improper cycling and the weapon may suffer reduced part
life for certain components.

[0006] Firearms such as the Remington M/1187 have self-compensating gas
systems. Self-compensating gas systems allow a wider range of loads to be
fired without requiring adjustment of the gas system. However, the wide
range of available cartridge loads may not be sufficiently compensated by
conventional self-compensating systems. For example, 12 gauge loads have
a wide spread from light 23/4'' loads to heavy 31/2'' loads. As a result,
some self-compensating designs may not reliably operate light loads under
all conditions, and may suffer undesirably high bolt velocities when
firing heavy magnum loads.

SUMMARY

[0007] According to a first example embodiment of the invention, a
gas-operated firearm comprises a receiver, a firing mechanism, a barrel
having a firing chamber, a plurality of ports extending through the
barrel and opening into the firing chamber, a bolt having a locking
position in which the bolt is adjacent a first, chamber end of the
barrel, and a gas operating system comprising a gas cylinder. The gas
cylinder has at least one piston bore in fluid communication with the
barrel through the plurality of ports in the barrel. The bores in the
barrel can be arranged as single ports or as groups of ports located at
different distances from the chamber end of the barrel.

[0008] According to one aspect of the present invention, the firearm is
capable of firing different cartridge loads, which generally correspond
to different cartridge lengths. The ports in the barrel can be arranged
so that when shorter, lighter load cartridges are fired, the cartridge
casing is short enough so that it does not interfere with, or render
"inactive" any of the ports in the barrel. The gases from firing
therefore pass unimpeded to the gas operating system and provide the
energy needed to perpetuate the action of the firearm. As longer
cartridges corresponding to heavier loads are fired, the cartridge case
may extend to a sufficient length within the chamber so that one or more
of the ports in the barrel are at least partially blocked, obscured, or
otherwise rendered "inactive" by the cartridge case. In general, the
heavier the cartridge load, the longer the cartridge, and accordingly a
greater number of ports are rendered inactive during firing of longer
cartridges. The larger the number of inactive ports, the smaller the
percentage of firing gases that are used to cycle the firearm. Heavier
load cartridges are therefore compensated for because the greater the
cartridge load, the smaller the percentage of the firing gases that is
passed to the gas operating system to cycle the firearm.

[0009] According to another aspect of the invention, the firearm is
capable of firing a wide range of shot loads without requiring active
adjustment of the firearm. The gases transmitted for cycling the firearm
are instead passively or automatically adjusted for according to the
length of the shell casing.

[0010] According to yet another aspect of the invention, any number and/or
combination of ports may be formed in the barrel, and corresponding ports
formed in the gas cylinder, in order to accommodate firing of a wide
variety of cartridge loads.

[0011] Other aspects, features, and details of embodiments of the present
invention can be more completely understood by reference to the following
detailed description of preferred embodiments, taken in conjunction with
the drawings figures and from the appended claims.

[0012] According to common practice, the various features of the drawings
discussed below are not necessarily drawn to scale. Dimensions of various
features and elements in the drawings may be expanded or reduced to more
clearly illustrate the embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0013] FIG. 1 is a partial sectional schematic view of a firearm having a
gas operating system according to a first embodiment of the invention.

[0014]FIG. 2 is an exploded view of the gas operating system according to
the first embodiment.

[0015]FIG. 3A is a perspective view of a gas cylinder of the gas
operating system.

[0024] FIGS. 5A and 5B are section views illustrating operation of the gas
operating system when firing a first cartridge type.

[0025] FIGS. 6A and 6B are section views illustrating operation of the gas
operating system when firing a second cartridge type.

[0026] FIGS. 7A and 7B are section views illustrating operation of the gas
operating system when firing a third cartridge type.

DETAILED DESCRIPTION

[0027] The invention as exemplified by the embodiment discussed below is
generally directed to a gas operating system for autoloading firearms.
The gas operating system allows a user to fire different loads for a
given shell caliber or gauge, while avoiding undesirably high bolt
velocities caused by firing excessive loads, and also ensuring that the
weapon cycles fully when firing lighter loads. The gas operating system
controls the amount of gas tapped from the barrel used to operate the
firearm action by controlling a number of "active" ports in the firing
chamber. An "active" port may be generally defined as a gas bleed port
that is at least partially unobstructed by a cartridge case and therefore
available to tap gases generated during firing. According to the present
invention, the gas ports may be located back in the chamber area of the
barrel. Cartridge cases of differing sizes and loads selectively cover
and render gas ports inactive according to the lengths of the cartridge
cases.

[0028] FIG. 1 is a partial sectional schematic view of a gas-operated
smoothbore shotgun firearm 150 incorporating a gas operating system 5
according to the first embodiment of the invention. The gas-operated
shotgun 150 includes a barrel 153 having a longitudinal bore 154 with a
longitudinal axis or centerline CL. The barrel 153 includes a cartridge
firing chamber 155 that is connected with a cylindrical portion 157 of
the barrel 153 by a frustoconical constriction portion 159. The
cylindrical portion 157 of the barrel 153 may extend to a muzzle end (not
shown) of the barrel. An example cartridge C is chambered within the
firing chamber 155. A bolt 161 is actuated by gas from a plurality of gas
ports, collectively indicated by the reference numbers 101 and 201, in a
manner described in further detail below. Each of the gas ports 101 of
the gas operating system 5 is aligned with a corresponding one of the
ports 201 in the barrel 153. The ports 101, 201 allow gases generated
during firing to be tapped from the firing chamber 155 to cycle the
firearm 150. In the exemplary illustrated embodiment, the bolt 161 has a
rotating head 163 which may be, for example, of the type described in
U.S. Pat. No. 4,604,942. Other bolt types may be used, and for the sake
of brevity, the operation of the bolt 161 is not repeated herein in
detail.

[0029] FIG. 1 is partially schematic in that several of the ports 101 and
the corresponding ports 201 in the barrel 153 are visible in the section
view of the cartridge firing chamber 155. As shown in further detail in
FIGS. 4A-4E and discussed below, the ports 101 are offset at different
radial and longitudinal positions in the gas operating system 5, and
therefore all of the ports 101 would not be visible in a single planar
section view. Each of the ports 201 in the firing chamber 155 is aligned
with one of the ports 101, and multiple ports 201 also would not be
visible in a single section view.

[0030] The gas operating system 5 includes a first and a second piston
pusher rod 10 (only one piston pusher rod 10 is shown in FIG. 1), a first
and a second gas diverter and cap 20 (only one is shown in FIG. 1), a
first and a second gas stop 50 (only one is shown in FIG. 1), and a gas
cylinder 100. The gas cylinder 100 may be attached to or formed as a part
of the firearm barrel 153. In the exemplary embodiment shown in FIG. 1,
the underside of the chamber 155 of the firearm 150 rests on an upper
surface of the gas cylinder 100 and the gas cylinder 100 is brazed to the
underside of the barrel 153. Each of the gas ports 101 formed in the gas
cylinder 100 is aligned with and in fluid communication with one of the
gas ports 201 in the barrel 153. The structure and operation of the gas
system 5 is described in further detail below.

[0031]FIG. 2 is an exploded perspective view of the components of the gas
operating system 5. The gas operating system 5 includes the first and
second piston pusher rods 10 (only one piston pusher rod 10 is shown in
FIG. 2), the first and a second gas diverters and caps 20 (only one is
shown in FIG. 2), the first and second gas stops 50 (only one is shown in
FIG. 2), and the gas cylinder 100. The gas cylinder 100 is generally
divided into first and second longitudinally extending sections 122, 124.
In the exemplary firearm embodiment shown in FIG. 1, the chamber 155 of
the firearm 150 rests on a cylindrical concave upper profile 118 of the
cylinder 100 that conforms to the shape of the underside of the barrel
153.

[0032] The piston pusher rods 10 each include an elongate cylindrical
piston body 12 having a plurality of spaced annular cleaning ribs 14 and
a head 16. The first piston pusher rod 10 is receivable and
longitudinally translatable within a rear end of a first longitudinal
piston bore 102 disposed in the first section 122 of the gas cylinder
100. The second piston pusher rod 10 (not shown) of similar or identical
construction to the first pusher rod 10 is receivable and translatable
within a rear end of a second longitudinal piston bore 104 disposed in
the second section 124 of the gas cylinder 100.

[0033] The first gas diverter and cap 20 is receivable within a front end
of the first longitudinal piston bore 102 and can be threadably engaged
with the piston bore 102 at threads 25. A frustoconical stem 22 extends
from one end of the diverter and cap 20, and is adjacent to an annular
recess 23 that is sized to receive an O-ring 40. The O-ring 40 provides a
gas seal for the cap and diverter 20 when mounted in the first piston
bore 102. The cap 27 extends from a front end of the cap and diverter 20
and includes peripherally-spaced bores 31. The peripheral bores 31 can be
provided, for example, to allow insertion of a tool used to screw and
unscrew the diverter and cap 20 from the piston bore 102. A longitudinal
lightening bore 29 may extend through the end of the cap and diverter 20.
The second gas diverter and cap 20 (not shown) of similar or identical
construction is receivable and threadably engageable within a front end
of the second longitudinal lightening bore 104.

[0034] The first gas stop 50 is receivable within a front end of a first
bleed bore 106 in the first longitudinal section 122 of the gas cylinder
100. A gas bleed slot 120 (see FIG. 1) is formed in a side of the first
section 122 of the gas cylinder 100, and is in fluid communication with
the first bleed bore 106. The first gas stop 50 extends from the front
end of the first bleed bore 106 and terminates short of the gas bleed
slot 120, as shown in FIG. 1. A second gas bleed slot 120 is formed in
the second section 124 of the gas cylinder 100, and is in fluid
communication with a second bleed bore 108 in the second section 122. The
second gas stop 50 of similar or identical construction is received in
the front end of the second bleed bore 108. The gas stops 50 may be
freely translatable within their respective bores 106, 108, and are held
in place by the cap and diverters 20 in the bores 102, 104 respectively.

[0035] According to one aspect of the invention, the plurality of gas
ports 101 are formed in the gas cylinder 100, in fluid communication with
the plurality of ports 201 in the barrel 153 (FIG. 1), and allow
cartridge loads of different "strength" to be fired from the firearm 150.
Three of the gas ports 101 are illustrated in FIG. 2, and are indicated
by the reference numbers 110, 112, 114. Additional gas ports 130, 132,
134 of the plurality of ports 101 in the gas cylinder 100 are illustrated
in FIGS. 3A-3C, and are discussed in detail below.

[0036]FIG. 3A is a perspective view of the upper surface of the gas
cylinder 100 illustrating the arrangement of the gas ports 110, 112, 114,
130, 132, 134 in the gas cylinder. FIG. 3B is a side elevational view of
the gas cylinder 100, and FIG. 3C is a top view of the gas cylinder. The
gas ports 110, 112, 114, 130, 132, 134 are arranged along the length of
the first and second sections 122, 124 of the gas cylinder 100, and
generally extend through the cylinder from the upper surface to a lower
surface of the gas cylinder 100. The upper ends of the gas ports 110,
112, 114, 130, 132, 134 are visible in FIGS. 3A and 3C.

[0037] Referring to FIG. 3B, the gas bleed slots 120 in the sections 122,
124 are spaced a distance D1 from a rear end of the gas cylinder
100. Referring to FIG. 3C, the gas ports 110, 112, 114, 130, 132, 134 are
staggered at three exemplary distances D2, D3, D4 from the
rear of the gas cylinder 100. The ports 112, 114, which are formed in the
first section 122, and the ports 132, 134, formed in the second section
124, are disposed at the distance D2 from the rear of the gas
cylinder 100. The port 110 is formed in the first section 122 and is
located at the distance D3. The port 130 is formed in the second
section 124 and is located at the distance D4. Cartridge shells of
different lengths may be selected to wholly or partially block, close
off, or otherwise cover one or more of the staggered gas ports 110, 112,
114, 132, 134, thereby rendering the closed gas port "inactive." An
inactive gas port is either wholly or partially ineffective in
transmitting gases generated during firing to the longitudinal piston
bores 102, 104, and therefore do not fully contribute to the rearward
forces on the piston pusher rods 10 (illustrated in FIG. 2) that force
the bolt rearwardly.

[0038] FIG. 4 is a bottom view of the gas cylinder 100 and illustrates the
bottom terminal ends of the gas ports 110, 112, 114, 130, 132, 134 in the
gas cylinder. As shown in the sectional views 4A-4C, the ports 110, 112,
114, 130, 132, 134 may be formed in the gas cylinder 100 at various
angular orientations.

[0039]FIG. 4A is a transverse section view taken on line A-A in FIG. 4
and illustrates the gas port 130 formed in the second section 124 and
located at the distance D4 from the rear end of the gas cylinder
100. The port 130 is oriented at an angle α with respect to a
vertical reference line. FIG. 4B is a transverse section view taken on
line B-B in FIG. 4 and illustrates the port 110 formed in the first
section 122 at the distance D3. The port 110 is oriented at an angle
β with respect to a vertical reference line. FIG. 4C is a transverse
section view taken on line C-C in FIG. 4 and illustrates the ports 112,
114, 132, 134 formed at the distance D2. The ports 112, 132 are
oriented at an angle γ in the respective sections 122, 124 with
respect to a vertical reference line. The ports 114, 134 are oriented at
an angle θ in the respective sections 122, 124 with respect to a
vertical reference line.

[0040]FIG. 4D is a transverse section view of the gas cylinder 100 taken
on line D-D in FIG. 4. FIG. 4E is a longitudinal section view of the gas
cylinder 100 taken on line E-E in FIG. 4. FIGS. 4D and 4E illustrate the
gas bleed slots 120 formed in the underside of the gas cylinder 100. The
gas bleed slots 120 can be formed by, for example, milling the underside
of the gas cylinder 100. Referring to FIG. 4D, the upper surface 118 of
the gas cylinder 100 can be generally concave cylindrical.

[0041] Firing of different cartridges using the firearm 150 and the
accompanying function of the gas operating system 5 is discussed below
with reference to FIGS. 1 and 5A-7B. For simplicity of illustration, as
in FIG. 1, FIGS. 5A-7B are partially schematic in that all of the ports
110, 112, 114, 130, 132, 134 in the gas cylinder 100 and the
corresponding ports 201 in the barrel 153 are shown or indicated by a
reference number in a single section view. As discussed above with
reference to 3A-4C, the ports 110, 112, 114, 130, 132, 134 are located at
different angular and longitudinal locations in the gas cylinder 100 and
all would not be visible in a single longitudinal planar section view. In
FIGS. 5A-7B, the ports 201 formed in the barrel 153 are numbered 210,
212, 214, 230, 232, 234 to correspond to the ports 110, 112, 114, 130,
132, 134, respectively, formed in the gas cylinder 100 with which they
are aligned and in fluid communication.

[0042] FIGS. 5A and 5B are sectional views illustrating operation of the
gas operating system 5 with a first cartridge type C1. In this example,
the cartridge C1 is relatively short in length, which generally
corresponds to a lighter load shell. Because the cartridge C1 is of
relatively light load, more of the gases generated during firing are
allowed to pass to the gas cylinder 100 to perpetuate the action of the
firearm 150.

[0043] Referring to FIGS. 1 and 5A, a shell C1 is loaded into the chamber
155 and the bolt 161 is closed, chambering the shell C1. The bolt head
163 locks to the barrel 153 or a barrel extension, if present. Locking
the bolt head 163 secures the cartridge C1 in the firing chamber 155
after the shell C1 is fired. In the illustrated example, the bolt design
is a rotating design, but other bolt types can be used. Generally
speaking, the shell C1 is fired by activating a firing mechanism, such as
by pulling a trigger to release a striker, which in turn hits the
cartridge primer (not shown). The primer is ignited and in turn ignites
the main powder charge in the shell C1. As pressure builds in the
cartridge case and the chamber 155, the wad and shot column travels down
the barrel 153.

[0044] As the shot column travels down the barrel 153, a percentage of the
high pressure firing gases in the barrel 153 is tapped and is introduced
into the gas cylinder 100. Referring to FIG. 5B, when the first cartridge
type C1 is fired, the case of the cartridge C1 assumes the extended form
C1' as the cartridge casing unrolls. In this example, the extended
cartridge form C1' does not cover or otherwise at least partially
obstruct any of the ports 210, 212, 214, 230, 232, 234 in the barrel 153.
All ports 210, 212, 214, 230, 232, 234 therefore remain active to
transmit gases through their corresponding ports 110, 112, 114, 130, 132,
134, respectively. Referring also to FIG. 1, gases transmitted through
the ports 110, 112, 114 are transmitted into the first piston bore 102
and force the first pusher piston rod 10 rearwardly against the bolt 161
in the direction of the arrow. Gases transmitted through the ports 130,
132, 134 are transmitted to the second piston bore 104 (not shown in FIG.
5B) and force the second pusher piston rod 10 rearwardly against the bolt
161. The gases generated during firing are therefore fully transmitted
through all of the ports 110, 112, 114, 130, 132, 134 (i.e., all ports
are active) to the first and second piston pusher rods 10 in the bores
102, 104, which provides the energy to unlock the bolt 161 and to propel
the bolt 161 rearwardly. As the pusher piston rods 10 move rearwardly and
uncover the gas bleed slots 120, the firing gases vent through the bores
106, 108 and the slots 120.

[0045] As the bolt 161 travels rearwardly, the spent case C1 is pulled
from the chamber 155 and ejected from the firearm 150. The bolt 161
travels to the rear of the receiver 201, which also compresses the action
spring (not shown). If no feeding shell is present in a magazine, the
bolt 161 locks open. If a feeding shell is present, the bolt 161 is
released from the rear position and is propelled forward by the stored
energy in the action spring. As the bolt 161 travels back toward the
barrel 153, a new shell is fed into the chamber 155 and the bolt head 163
locks to the barrel 153. The cycle repeats when the trigger is again
pulled.

[0046] FIGS. 6A and 6B are sectional views illustrating operation of the
gas operating system 5 with a second cartridge type C2. In this example,
the second cartridge type C2 is longer than the first cartridge C1, which
generally corresponds to a heavier load shell. Because the cartridge C2
is of heavier load, a smaller portion of the gases generated during
firing are communicated to the gas cylinder 100 to perpetuate the action
of the firearm 150.

[0047] The cartridge C2 is fired in generally the same manner as the
cartridge C1. Referring to FIG. 6B, as the cartridge C2 is fired, the
case of the cartridge C2 extends as it unrolls and assumes the form C2'.
The extended case C2' at least partially covers the ports 212, 214, 232,
234 in the barrel 153, rendering them inactive. The gases generated
during firing are therefore either wholly or partially blocked from
passing into the gas cylinder 100 through the corresponding ports 112,
114, 132, 134 in the gas cylinder 100 with which the ports 212, 214, 232,
234 are in fluid communication. The other ports 210, 230 in the barrel
153 remain active, and the firing gases are allowed to pass through the
corresponding ports 110, 130 and into the first and second piston bores
102, 104, respectively. The gases transmitted to the first and second
piston bores 102, 104 provide the energy required to force the pusher
piston rods 10 rearwardly to cycle the firearm 150, as discussed above.

[0048] FIGS. 7A and 7B are sectional views illustrating operation of the
gas operating system 5 with a third cartridge type C3. In this example,
the third cartridge C3 is longer than the second cartridge C2, which
generally corresponds to a heavy load shell. Because the cartridge C3 is
of heavy load, a relatively small portion of the high pressure gases
generated during firing are communicated to the gas cylinder 100 to
perpetuate the action of the firearm 150.

[0049] The third cartridge type C3 is fired in generally the same manner
as the cartridges C1 and C2 discussed above. Referring to FIG. 7B, as the
cartridge C3 is fired, the case of the cartridge C3 extends as it unrolls
and assumes the form C3'. The extended case C3' at least partially covers
or otherwise obstructs the ports 212, 214, 232, 234, 210 in the barrel
153, rendering them inactive. The gases generated during firing are
therefore either wholly or partially blocked from passing into the gas
cylinder 100 through the corresponding ports 112, 114, 132, 134, 110 in
the gas cylinder 100 with which the ports 212, 214, 232, 234, 210 are in
fluid communication. Only the port 230 remains active, and gases are
transmitted through the corresponding port 130 in the gas cylinder 100
and into the second piston bore 104. The gases transmitted to the second
piston bore 104 act on the second pusher piston rod 10 to cycle the
firearm 150 as discussed above. In this mode of operation, only one
pusher piston rod 10 is used to cycle the firearm 150.

[0050] According to one aspect of the present invention, the gas operating
system renders a firearm capable of firing a wide range of shot loads
without requiring active adjustment of the firearm. The gases transmitted
for cycling the firearm are instead passively or automatically adjusted
for according to the length of the shell casing. Any number and/or
combination of ports may be formed in the barrel, and corresponding ports
formed in the gas cylinder, in order to accommodate firing of a wide
variety of cartridge loads.

Example

[0051] A firearm 150 is provided with a gas operating system 5 as
illustrated in FIGS. 1-7B. The gas cylinder 100 has a length, measured
from left to right in FIG. 4, of 77 mm. The distances illustrated in
FIGS. 3B and 3C are: D1=30.2 mm, D2=43 mm, D3=49 mm, and
D4=62 mm. The angles illustrated in FIGS. 4A-4C are:
α=25°, β=25°, γ=25°, and
θ=42°. Each of the ports 110, 112, 114, 130, 132, 134 are
cylindrical bores having a diameter of 1.2 mm. The ports 210, 212, 214,
230, 232, 234 are also cylindrical bores. The piston bores 102, 104 are
cylindrical bores having a diameter of 10.8 mm. The bleed bores 106, 108
are cylindrical bores having a diameter of 5 mm. The exemplary cartridge
C1 illustrated in FIGS. 5A and 5B corresponds to 23/4 inch 12 gauge
ammunition. The exemplary cartridge C2 illustrated in FIGS. 6A and 6B
corresponds to 3 inch 12 gauge ammunition. The exemplary cartridge C3
illustrated in FIGS. 7A and 7B corresponds to 31/2 inch 12 gauge
ammunition.

[0052] In the embodiment described above, the barrel 153 is illustrated as
formed separately from the gas cylinder 100, and gases generated during
firing are communicated from the chamber 155 through aligned sets of
ports in the barrel 153 and the gas cylinder 100. In an alternative
embodiment, the gas cylinder and the barrel may be of a one-piece
construction, requiring only one set of ports.

[0053] The gas cylinder 100 described above is divided into two sections
122, 124, which house two separate piston pusher rods 10 in a "dual-tap"
configuration. A "single-tap" system, using a single piston bore with a
single piston pusher rod, is also within the scope of the present
invention. In this embodiment, bores formed in the firearm barrel would
each be in fluid communication with the single piston bore.

[0054] The components of the gas operating system 5 can be made from
conventional durable, high strength materials including metals, such as
hardened steel, composites, and other materials.

[0055] In the illustrated embodiment, the ports 110, 112, 114, 130, 132,
134 in the gas cylinder 100 and the corresponding port 210, 212, 214,
230, 232, 234 in the barrel 153 are straight along their lengths and
circular in cross section. The ports may, however, take the form of other
apertures, such as, for example, apertures of non-circular cross section.

[0056] The ports 110, 112, 114, 130, 132, 134 in the gas cylinder 100 and
the corresponding ports 210, 212, 214, 230, 232, 234 in the barrel 153
can be formed by methods such as drilling, for example. In one exemplary
method of manufacture, the gas cylinder can be brazed to the barrel
before forming the gas tap ports. Each port in the gas cylinder (e.g.
port 110) and its corresponding port in the barrel (e.g. port 210) can
then be drilled in a single drilling operation. In order to facilitate
drilling, slots or other locating features may be milled or otherwise
formed at one or more locations on the underside of the gas cylinder so
that a drill bit can be readily located on the exterior of the gas
cylinder. When viewed from the perspective of FIG. 1, the ports 110, 112,
114, 130, 132, 134 in the gas cylinder 100 and the corresponding ports
210, 212, 214, 230, 232, 234 in the barrel 153 are illustrated as
extending perpendicular or substantially perpendicular to the long axis
CL of the barrel 153. The ports may, however, be oriented at other
nonzero angles with respect to the long axis CL of the barrel.

[0057] The example embodiment of the gas operating system 5 is
incorporated in a gas-actuated twelve-gauge shotgun. Other types of
gas-actuated firearms may be equipped with a gas operating system as
discussed herein without departing from the scope of the present
invention.

[0058] The gas ports disclosed in this specification are described as
formed by drilling. Any of the ports in this specification can be formed
by alternative methods, such as, for example, electronic discharge
machining (EDM).

[0059] The method of operating the firearm 150 is described in terms of a
trigger-operated firing mechanism that releases a striker. Other types of
firing mechanisms, such as, for example, electrical firing mechanisms,
can also be incorporated in a firearm in accordance with the present
invention.

[0060] The foregoing description of the invention illustrates and
describes the present invention. Additionally, the disclosure shows and
describes only selected embodiments of the invention, but it is to be
understood that the invention is capable of use in various other
combinations, modifications, and environments and is capable of changes
or modifications within the scope of the inventive concept as expressed
herein, commensurate with the above teachings, and/or within the skill or
knowledge of the relevant art.